Gangliosides appear to be important recognition molecules on the cell surface. The membrane receptor for cholera toxin is the ganglioside GM1. The turnover of GM1 is blocked in cells exposed to the toxin. The turnover of the two components of the toxin are dramatically different. The B component, which binds to GM1, is metabolized much slower than the A1 component, which activates adenylate cyclase. Butyric acid induces cholera toxin receptors in several cultured cell lines. The increase in toxin binding corresponds to an increase in GM1 content. Gangliosides inhibit the attachment of cells to collagen; cell attachment is mediated by fibronectin, a cell surface glycoprotein. The most effective inhibitors are GT1 and GD1a. The gangliosides have been shown to interact directly with fibronectin.